Disposition of alendronate following local delivery in a rat jaw

Background: Recently, we have shown that local delivery of alendronate reduced significantly bone resorption activated by surgical separation of periosteum from bone. These results advocate the use of local application of alendronate in bone surgeries to prevent regional bone resorption at the surgery site. Here we investigated the efficacy of absorbtion of alendronate by the bone from a gelatin sponge soaked with radiolabeled alendronate applied topically at the surgical site. Methods: Following elevation of the mucoperiosteal flap next to premolars and molars of the rat mandible, a gelatin sponge soaked with 10 mu l of radiolabled alendronate (1 mu Ci/mg) was applied to exposed bone on one side. The local absorbtion of alendronate and its disposition in the contralateral side of the mandible as well as in the tibia bone were analyzed. Results: The results show that 10% of total alendronate content of the gelatin sponge was absorbed in the bone locally (in the surgical site), while 0.2% was disposed in the tibia. Of interest is the fact that the surgical wound in the contralateral side increased the disposition of alendronate up to 2%. This finding is most likely the result of extravasation and diffusion of alendronate due to surgical wounding. Conclusion: This study strongly supports our notion that local delivery of alendronate and its affinity to bone may become a very important treatment modality to prevent resorption of bone during dental and orthopedic procedures.